Headliners for vehicles are conventionally constructed of fiber glass or multi-layered laminated panels incorporating fiber glass and foam resin layers. In the conventional manufacturing process, the layers are placed between mirror image mold surfaces, compressed, heated to cure an incorporated thermosetting resin, and then cut to shape at their periphery. Sometimes apertures for window openings, light fixtures, sun visors and the like are cut in the panels after molding. More often than not, in the assembly of the vehicle the headliner is inserted through the front window before the windshield is mounted. The typical headliner is in the shape of a dome with the concave surface facing downward. It is sufficiently rigid to hold its shape when mounted in the passenger compartment and supported along its side edges with the central part of the headliner juxtaposed to the roof.
Various problems exist in the assembly of the headliner and one of those problems is that the headliner includes a decorative layer as the exposed surface visible to the passengers. Any folds, creases or blemishes in the visible surface creates a problem for one marketing the vehicle. As a practical matter, it is unacceptable to have exposed blemishes. Also, breakage is a problem due to brittleness of the cured structure.
The headliner serves three other functions in addition to aesthetics which may be at odds with the concern for exposed blemishes. One function is to provide a soft surface to minimize injury with head bumps. Fiber glass headliners are hard as are conventional headliners incorporating foamed resin and do not provide much padding for one's head. The only cushioning is in the decorative fabric which may or may not have a soft foam backing. A second function is to provide insulation from heat between the roof of the vehicle and the interior or passenger compartment. The third function is to provide sound insulation from exterior wind noise, engine noise, and the like.
A common solution to the problem of heat and noise insulation is to use foamed resin layers in the headliner. The foamed resin is a better heat and sound barrier than resin impregnated fiber glass. Unfortunately, the foamed resin most often used is of the "closed cell" variety which includes a plurality of bubbles throughout the resin. Such foamed resin is initially quite rigid and with a sealed skin coating it is even more rigid. Therefore, when the headliner must be bent or folded out of its original molded shape to get it into the proper position for installation in the vehicle it often cracks and/or ruptures bubbles within the foamed layer itself. This often leaves a crease in the headliner which is visible through the fabric. That is also true of fiber glass headliners. Exposed creases are a problem because an exposed crease makes the flawed headliner unusable from a practical standpoint. As a consequence of the problem, the size of the windshield opening is often dictated by the size of the headliner which must be inserted (whether the vehicle manufacturer knows it or not). Making the windshield opening larger minimizes deflections of the headliner to get it in operative position.
A patent to Steward et al, U.S. Pat. No. 4,211,590, discloses a process for manufacturing a headliner for a passenger vehicle and the laminated contoured headliner includes one or more foamed resin thermoplastic layers of the closed cell variety sandwiched between a pair of rigid thermoplastic skin coats.
A patent to Harayama et al, U.S. Pat. No. 4,721,643, discloses another process for making a headliner and it too discloses a thermoplastic foamed resin layer of closed cells. The disclosure describes a laminate of a plurality of layers but all are structured so that there is a surface skin layer at each boundary of each foamed resin layer which inherently makes for rigidity and crease problems in assembling the headliner.
A patent to Landler et al, U.S. Pat. No. 4,478,660, discloses a different laminate and different process for making a foamed resin layer in a decorative panel but it is even more rigid than the headliners described above because of the incorporation of a hardenable resin mixed with wood dust filler in one layer.
A patent to Breitscheidel et al, U.S. Pat. No. 4,826,552, discloses a process for making a panel using an elastomeric, fiber glass reinforced, foam and a polymer substrate. It is clear from a reading of the patent that the rigidity of the resulting panel makes it inappropriate for a headliner.
The product on the market which is currently being used for headliners which is similar to the instant invention is a laminated panel which includes a decorative fabric layer for its exposed surface and the fabric is bonded directly to a closed cell foamed resin layer, the layer being coated on both sides with a hard resin skin. The next layer is a fiber glass mat which is sandwiched between the aforementioned foamed resin layer and another which is essentially identical. The backing layer is scrim. In both cases the closed cell foam used is coated on both sides and has an industry designation "120 ILD". The panel is relatively rigid and a fold results in a permanent crease clearly visible through the fabric layer. More recent products substitute open cell foamed resin panels which are impregnated with an isocyanate resin and an amine catalyst. The problem with that combination is that the amine catalyst (1) may be toxic at low concentrations and (2) where the vehicle sits in the summer sun, the heat "boils" the amine out of the laminate and it coats the windows as a fog.
A patent to Satterfield et al, U.S. Pat. No. 5,007,976 discloses a means to minimize fold-crease propagation to the fabric face by providing a laminated panel which is sufficiently flexible that it does not show a crease at the fabric surface even if the panel is folded three or four times over itself. This property is accomplished by using an open cell foamed thermoplastic resin of polyurethane rather than the closed cell thermoplastic resin or the isocyanate resin-open celled combination used by the prior art. Additionally, a special adhesive mixture is used to bond the layers of material together. The adhesive is a blend of about two-thirds polyol, about one-third isocyanate, and a catalyst.
One open celled, foamed resin layer near the decorative fabric is uncoated with the adhesive and as a consequence gives the fabric surface a soft feel, due to the open cell structure. It serves the purpose of absorbing the shock of a head bump without head injury. A second open celled, foamed resin layer is located near the roof of the vehicle and it is saturated with the adhesive. The adhesive hardens during curing and the back or outermost surface of the laminate feels hard.
Within the laminate are two layers of a fiber glass mat. The two fiber glass layers are separated by other layers within the laminate and the random orientation of the fibers serves to strengthen the panel in tension in all directions.
The laminate further includes a plurality of woven layers which are known as "scrim" and "reemay", terms that are well known in the industry.
The Satterfield et al patent is commonly owned and a significant technical advancement over prior panels. However, the labor intensive aspects of its assembly create cost problems and certain disclosed materials are not adequate in certain circumstances.
The term "scrim" as used in this application refers to a thin woven or non-woven fabric not unlike cheese cloth which is formed of cotton fibers or other materials having appropriate wetting qualities to assure a proper bond with the liquid adhesive used.
As used in this application the term "reemay" refers to a mat of non-aligned fibers of spun polyester which adds strength to the overall structure.